This application claims the benefit of Korean Application No. 68345/97, filed Dec. 12, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and a method for compensating for the temperature of a laser diode in an optical disk field, and more particularly, to an apparatus and a method for compensating for the temperature of a laser diode in which output power changes according to the variation of the temperature.
2. Description of the Related Art
It is possible to read information from a disk without error only when light is stably emitted from a laser diode. This is achieved by controlling a luminous efficiency which changes according to the variation of the temperature of a narrow-wavelength laser diode in an optical disk field. Accordingly, it is possible to heighten the reliability of an optical recording and reproduction system.
FIG. 1 is a block diagram showing a conventional temperature compensation apparatus of a laser diode. In FIG. 1, the output of a laser diode 11 is converted into a voltage signal by a photodiode 12. An amplifier 13 amplifies a very low voltage output from the photodiode 12 to a signal level. A voltage comparator 14 compares the voltage amplified by the amplifier 13 with a reference voltage, and generates an error signal. Here, the reference voltage is generated by a reference voltage generator 15 and is previously set.
An up/down counter 16 up-counts (xe2x80x9cincrementsxe2x80x9d) and down-counts (xe2x80x9cdecrementsxe2x80x9d) based upon the comparison of the error signals and generates an error voltage by correcting the error signal. A digital-to-analog converter 17 converts the corrected error voltage into an analog voltage signal. A current amplifier 18 converts the analog voltage signal into a current signal for driving the laser diode 11 and applies the current signal to the laser diode 11. The output power of the laser diode 11 is controlled by continuously performing such an operation.
However, it is hard to control the variation of the optical output of the laser diode due to temperature by using only the up/down counter 16, since the variation of the temperature is severe in the narrow-wavelength laser diode. Therefore, it is impossible to compensate for the variation of the optical output by the conventional apparatus shown in FIG. 1.
To solve the above problem, it is an object of the present invention to provide a temperature compensation apparatus of a laser diode in which it is possible to reduce a control error by extending the range of the control voltage of the laser diode, considering deterioration due to the variation of the temperature of the laser diode.
It is another object of the present invention to provide a temperature compensation method of a laser diode, for stabilizing a luminous efficiency by extending the range of the control voltage of the laser diode, considering the deterioration due to the variation of the temperature of the laser diode.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the first and other objects of the present invention, there is provided a temperature compensation apparatus of a laser diode, for controlling the output power of a laser diode according to the variation of a temperature of the laser diode, including a first generator to generate an error voltage between a voltage corresponding to the output power of the laser diode and a reference voltage and a second generator to generate a corrected control voltage by receiving the error voltage, based on the output power and to output the corrected control voltage to the laser diode for a predetermined period of time when the error voltage overflows or underflows.
To achieve the second and other objects of the present invention, there is provided a temperature compensation method of a laser diode, for controlling the output power of a laser diode according to a temperature change of the laser diode, including the steps of (a) generating an error voltage between a voltage corresponding to the output power of the laser diode and a reference voltage and (b) generating a control voltage by correcting the error voltage based on the output power and extending the range of a control voltage by outputting a corrected control voltage to the laser diode for a predetermined period of time when the level of the error voltage overflows or underflows.